I will make five points here. First, the word “enlighten” means “to give knowledge.” Here it is “knowledge of salvation,” since those who receive the true Light become the sons of God (1:12). On the other hand, those who reject Him will be lost (3:19). Second, the enlightenment that comes from God is gracious because it is undeserved and redemptive. Third, it the Holy Spirit who illuminates all people. Although John does not mention the Holy Spirit here, he refers to the Spirit’s universal work later (16:7-8) and Christians have always connected His work to John 1:9. Fourth, I understand Romans 3:23 and Isaiah 53:6 to mean that every person has rejected the light. But, finally, this does not change God’s desire for all to be saved nor His effort to save them (2 Peter 3:9). These five reasons are why Wesleyans have cited John 1:9 more frequently than any other Scripture in support of “prevenient grace,” the doctrine that God gives grace to all people whereby they may be saved.
Calvin did not hesitate to limit the scope of the light that comes from God. He said that the heathen who are not chosen for salvation receive enough light to condemn them but not enough to save them.
But Jesus said, “If any man will do his will, he shall know the doctrine.” Apparently, if a person honestly seeks God, God will tell him what he needs to know.
In Scripture we find examples of those reached by God’s grace without contact from either Israel or the church. Job was upright and rejected evil before Moses lived and before a page of Scripture was written. Balaam was in relationship with God and was known as the seer who got messages from God without going into a trance. Abimelech put Abraham to shame after Abraham thought, “Surely the fear of God is not in this place.” The Holy Spirit brings the light of Jesus even to those who have not heard of Him.
Adam Clarke declared that Christ’s atonement made all men salvable. I don’t know how God enlightens every man, but I believe that, being both just and merciful, He does. So do these commentators:
“We must not suppose that all light of faith, of hope, of justice, of purity, of truth, first dawned on the world when Christ came. [He] has been in the world ever since there was one, . . . working everywhere before His appearance, and whatever light of truth there has been at any time has come from Him” (H. F.Beecher, Biblical Illustrator).
“He who first said, ‘Let there be light!’ having provided that which is natural, did not withhold that which is spiritual” (Pulpit Commentary).
Whether it be the light of nature, reason, conscience, or some special revelation, Jesus is its source. And as one writer said, “That Christ, the true Light, should dart His beams downwards to this abiding-place of sin is part of the wonderfulness of the gospel which we preach.”
We believe that God’s prevenient grace draws every person. God has revealed Himself to us in many ways: General revelation (creation, nature, etc.); Special revelation (Holy Scripture); and, Living revelation (Jesus Christ, who fully, perfectly revealed who God is, Hebrews 1:1-3).
Each person’s level of knowledge may be different, but the Light is the same. Because God is not willing that any should perish, isn’t it likely that He is at work in dark places shining His Light?
When anyone responds to the Light, God will give him more Light. Even if God has to send an angel or Jesus (as stories suggest) to reveal important truths to him, God will save anyone who seeks Him with his whole heart (Jeremiah 29:13). People will not be saved because of ignorance, as some suggest. If some are saved, it will be by grace through faith in Jesus. They can put faith in Christ - genuine trust that results in obedience - without knowing everything about Him.
In Don Richardson's classic writing "Eternity in Their Hearts" we see that God has planted the seed of spiritual truth in every man's heart. Where did man get the "idea" to worship something? The revelation of Jesus to the heathen via nature (creation) has been rejected by the heathen: "Because that which may be known of God is manifest in them; for God hath shewed it unto them. For the invisible things of Him from the creation of the world are clearly seen, being understood by the things that are made, even His eternal power and Godhead; so that they are without excuse.” Romans 1:19-20.
In short, the answer is found in Psalm 19:1-4: “The heavens declare the glory of God; and the firmament showeth His handiwork. Day unto day uttereth speech and night unto night showeth knowledge. There is no speech or language, where their voice is not heard. Their line is gone out through all the earth, and their words to the end of the world....”
He lights all men by being the ideal light, the perfect and embodied illustration of truth. Any lesser light would ultimately lead men astray into darkness.
All men receive light by Jesus because, through creating and sustaining the universe, he reveals the nature of God to those who inhabit it. All men receive light through Jesus because each one enters his earthly life bearing Christ’s image in himself. This very image ensures a moral consciousness in every man. Jesus lights all men through the Person of the Holy Spirit whose ministry it is to reveal Christ and to reprove the world of sin, righteousness and judgment. Finally, Jesus’ light falls on all men to the degree of their faith. Wherever men are found, if they accept by faith the general revelation of creation and conscience, Jesus will use various methods, including dreams, visions, miracles, and missionaries to bring them explicit revelation of His divinity and personal Lordship over their lives.